They tend to do lots of tests and very quickly when it comes to eye stuff. Mainly I think because all the structures are very small and small changes can be caused by lots of different things. Most of which are completely harmless.
I have a load of crap wrong with my eyes, the right one is basically just there to fill a whole at this point. Since I was 4 I have been referred back and forth from opticians to the hospital at the drop of a hat. Must have had at least a dozen urgent referrals, have had every type of eye test, scan, MRI, electrodes all over my head and faces dye injected for contrast imaging, surgery. You name Tim they’ve tested it. Most of the stuff they have suspected has proven to not be the case, but they have to rule them out.
On the topic of the MRI specifically though, it is worth prepping your son a little. It’s not in any way painful but it is loud, can take about 20 mins and the space is confined so it can feel discomforting. He also needs to make sure he has no metal on him, so if he’s going through any kind of nail polish, studded jewellery, piercing or eyeliner phases, he’ll need to go metal free that day.
things they have suspected and then not found for me include but are not limited to:
Brain tumour
Morning Glory Syndrome
Optic Neuritis
Blood clot/aneurysm
Actual eye problems I do have
Coloboma of Optic Disc
Coloboma of retina
Serous Macula Detachment - now fixed following reattachment surgery
Astigmatism
Very short sighted